Hormone replacement therapy (HRT) can be useful for preventing osteoporosis and improving serum cholesterol levels among postmenopausal women. However, postmenopausal HRT is associated with minor adverse events, such as abnormal vaginal bleeding and breast pain or discomfort, and may be associated with increased risks of breast and uterine cancer. OBJECTIVE: To compare resource utilization for uterine and breast disease screening, diagnostic evaluation, and treatment among postmenopausal HRT users to non-HRT users, over a two-year period. METHODS: The study uses 1993-96 MarketScan? data. Women at least 50 years old were identified as new HRT users based on both an estrogen and a progestin claim within 45 days of each other, with no evidence of either therapy during the prior six months. The sample of HRT users included 970 women. A random sample of 2,236 women with no HRT use over the study period was selected as a control group. RESULTS: HRT users were more likely than non-users to have visits with each of the following diagnoses: postmenopausal bleeding, metrorrhagia, dysfunctional or functional uterine hemorrhage, or abnormal bleeding from the female genital tract. HRT users were more likely to have uterine-related procedures such as ultrasound or hysteroscopy, and more likely to have some breast-related procedures, such as mammography, ultrasound of the breast, biopsy of breast, or drainage of cysts. CONCLUSIONS: Postmenopausal HRT recipients were more likely to experience abnormal uterine bleeding and to have procedures related to uterine bleeding. Future evaluations of the cost-effectiveness of HRT as a long-term prevention strategy should incorporate the costs of resource utilization related to adverse events of HRT in addition to its clinical benefits.